Risk assessment by fault tree analysis of methane explosions in Turkish hard coal enterprises underground mines

Mevsim, Rıdvan
Mining is one of the most hazardous industries in the world. Among all mining professions, underground coal mining has the highest occupational accident and disease rates. Methane explosion appears as the major accident type which results in severe loss of life and property in underground coal mining. Including underground coal mines, preparing a practicable risk assessment is the primary step to sustain a safe workplace environment. The main objective of this study is to specify the root causes of methane explosions in underground hard coal mines by performing quantitative risk assessment. Total of 67 methane explosions resulted in 815 fatalities between the years 1875 and 2014 within Turkish Hard Coal Enterprises (TTK), which is the major hard coal producer in Turkey, are evaluated in order to achieve the goal. A deductive risk analysis technique, fault tree analysis (FTA), was implemented in order to specify the root causes of methane explosions. The methodology starts with examining the occupational accident statistics gathered from TTK. Using the data, events and gates of the fault tree were constructed by a step-wise approach. Major and minor causes of methane explosions were identified by utilising ReliaSoft BlockSim-7 software. Research findings revealed that mechanical ignitions are the most significant failure event for a possible methane explosion. It is followed by deficient ventilation practice, methane outburst, blasting, and electrical ignition, respectively. The time period in which a methane explosion has a 100% probability to occur was found as 108 months. Excluding the most significant failure event mechanical ignitions from the fault tree, the period increases to 255 months. Besides the quantitative FTA, also qualitative FTA was conducted. Qualitative fault tree has 27 intermediate events and 65 basic events (root causes) which make it a comprehensive fault tree of methane explosions among other studies in the field. This study, as being the first implementation of FTA for methane explosions in Turkish underground coal mines, is expected to contribute to mining industry and current literature in various ways. Research area could be extended in the future studies from TTK to Turkish coal mining industry, including also the private sector companies. The monotype 5 x 5 matrix risk analysis practice in the country could be improved by raising the awareness of coal industry to the comprehensive nature of FTA approach and performing FTA at mining companies. A general guide to prevent methane explosions could be prepared by considering the root causes on the fault tree and it could also contribute to the provisions of national occupational safety and health legislation. The ultimate goal is to prevent possible accidents caused by methane explosions.